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Discussion in 'Northeastern US Wireless Forum' started by MeatChicken, Jun 4, 2004.
I wish all carriers could have 800/1900 overlay systems.
Might also be Verizon in your area is starting to max call capacity?? Sprint is not?
probably the real difference is the wireless phone.
It is common knowledge that Sprint sounds better than Verizon, but 1900 and 800 are not the only differences between Verizon and Sprint. Verizon is probably using EVRC in a more conservative mode in order to preserve capacity which cuts down voice quality.
It's because 1900 MHz has more Bandwidth than 850 MHz. This is the advantage of 1900 MHz over 850 MHz, allowing for more capacity room.
It may also be the type of phone is being used. When a friend of mine had a Sanyo 4900 and some older LG candybar phone his call quality was horrible on Sprint. I also have a couple friends on Verizon with the LGVX6000 and I can't tell if they are calling me from a landline or a cell unless I check my caller ID.
So could you say that because the PCS channels allow more capacity, the voice quality is not strained as often as on a cellular system? Because with CDMA, higher traffic kills voice quality....
I guess that makes sense given what bobolito is saying also...although they aren't really the same argument they both point to pcs supporting more capacity so voice quality is then better...
i don't think it is the phone. IMO verizon has always sounded worse than Sprint. Here iN DC, I think the best voice quality belongs to TMO,
Any news when 1900 will launch? How will laymen like myself know when it's on?
That is not the reason. CDMA uses 1.25Mhz channels no matter what frequency it is running on. The reason is the codec Verizon and Sprint use are in different operational modes.
As for Verizon, not only did they have to install 1900Mhz in all their 850Mhz sites. They also had to install 1900-only sites in intermediate spots so the 1900Mhz service is continuous. Pretty much the same thing AT&T already did.
What i mean is you can fit alot of 1.25 MHz channels in their 1900MHz License than in their 850MHz band.
That's why my analogy is a big room and a small room, You can fit alot of people in a Big room than a small room.
I am hearing "August" , but things can get delayed
I am sure that it will be sometime between August & November at the latest.
Jones: Both VZW & ATT have 10Mhz of 1900Mhz, so they can actually "fit" more channels into their 800Mhz band....
Thanks for the Info, Guys.
I guess once they turn on their 1900 it would handle more calls.
But why, with CDMA, would the 1900MHz coverage need to be continuous? I thought the whole idea was to use 1900MHz to supplement the exisisting voice channels. It they already have a 800MHz built network, then the 800 band with longer reach should be able to cover the 1900 induced gaps with seamless handoff between 1900 and 800.
The only reasons to add new fill-in 1900MHz sites I can think of would be:
1) to cover pre-existing gaps on the 850MHz network, or
2) because data will be on 1900 only and they need continuity for that reason.
From what I heard from my VZW contact, as of right now they are Not putting up any 1900Mhz-Only sites, but concentrating on getting all their existing sites up & running as Dual Banders as you suggest. Who knows what they will do in the future.
Unlike what AT&T did with their NY GSM 1900, VZW is not building "another" system seperate from their 800Mhz CDMA, so their is no immediate pressing need for 1900-Only sites.... Also, in "some" (a "surprising few", Not All!! ) areas, VZW's cell spacing is already the envy of 1900Mhz carriers!
As to your 2nd point about "seamless" handoffs.... I'm not sure about that.
It is my understanding from speaking to techs, that, when using a "single band" (say, 1900Mhz), normally as your phone reaches the "end of coverage" of one cell, another cell is already receiving the signal, & the system "knows" which cell/panel to handoff the call to.
With a company that overlays 1900 & 800, (ATT & VZW), a phone that is "transmitting on one band" (1900Mhz), can't simultaniously be xmitting on the other, so in the case of a 1900 call comming to the end of the sites range, if their is no other 1900Mhz cell receiving the signal, there would be either a dropped call, or a "blind" handoff to an 800Mhz channel based on some sort of "guess" that the switching computer feels is correct.
This dual ovelay stuff is a "grey area' that I would like to know more about.
Bobolito - Have you had any 1st hand experience going from 1900 to 800 & back, while on the same call?? (indoor/outdoor or whatever)....
Yes, AT&T GSM does it all the time. One minute you are on 800, the next you are at 1900. Actually, there are some AT&T towers that have 1900Mhz control and voice channels and at 800Mhz only voice channels. The phone switches constantly between 1900 and 800 many times per second and it is all totally seamless and unnoticeable to the user. With CDMA, it might be a little more complicated to do that because CDMA normally uses soft-handoffs that don't change channels so the phone is usually on the same frequency all the time. An interband handoff would mean the phone is actually performing a hard-handoff like TDMA/GSM because there is a frequency change. However, the same thing happens when you are driving and you go across markets and your phone has to switch from the A to B band even if it is all at 800Mhz. An example is when crossing from CT into NY on I-95 or the Merrit Pkwy. because Verizon is band A in CT and band B in NYC.
Now, I agree that for voice calls a seamless 1900Mhz coverage is not necessary for Verizon in this area. However, if they later on decide to deploy EV-DO at 1900Mhz, people won't be happy with the coverage holes.
Yes, I do realize that it would have to be a hard handoff, since simultaneous multi-cell calls can't happen with cross-band.
Does anyone know if You are currently able to Cross-Band Roam??
I understand that, for example, crossing into CT, you are still on VZW, but what if you are crossing into a Sprint or Alltel extended roam area??
The VZW system can't possibly "control" a channel of a neihboring Sprint or Alltell site, (especially if on another band), & I would imagine the call would be dropped..... Same I guess with The other carriers when they use a roam partner....
I don't know if this got answered
if you get all circuits are busy means mobile switching station somewhere is full
fast busy signal means you are not connecting to the tower.
bad signal or tower does not have any free channels open to call.
Meatchicken, if you have to cross to roam into another carriers network, then most of the times your call will drop. However, if they set it up, it wouldn't be the first time. I know areas where you can drive across license borders and you can pass your call from AT&T into Cingular and vice-versa and not drop the call. This has existed long before Cingular was born. There isn't really a problem handing off across bands. That is the least of the problems. A cross-band handoff is no different than handing off from one tower to the other in the same band because it is just a channel switch just like any other. The most challenging problem is getting two different carrier networks to talk to each other so that the handoff is performed correctly.
AgentHibby, if you get a message on the screen saying "System Busy" or no response from the tower (sometimes a fast high-pitched busy tone) this means the tower is probably too busy to handle anymore users. However, if you hear any recorded message, of course you have acquired a voice channel because you have to connect to the tower first before you can hear anything on your phone. This means the tower is not full. If the recorded message says the circuits are busy, that usually means there are no more lines available at your local switch to carry the call out into another area or network. If the recorded message says that the number you are calling is busy, it probably means that the switch in the other end is the one having the overload problem.
Hmmm....don't know how to subscribe to a thread withoughty posting to it.
I wonder how much this will help in times Square.
Bobolito: I just caught this from your last post.
Are you saying AT&T is handing off your call to 800 & 1900 panels, back & forth multiple times per second??
That doesn't seem right, & what would be the sense of a carrier doing hard handoffs multiple times per second?? How can the phone's test screens even show a call's voice channels being handed off / switching in fraction of a second increments... or what am I missing here??
It's called "Frequency Hopping" one of the features GSM employs for security and dynamic spectrum allocation. They are not handoffs because they happen within the same tower. Normally, this is done by spanning across an entire spectrum band or the spectrum share allocated to the tower. So, in my example above, this is a tower that has both 800 and 1900 and while it is hopping, the phone will rapidly switch between 800 and 1900. The result is some time slots are delivered at 800 and others at 1900. T-Mobile does the same thing but only on 1900, of course. My phone can be constantly switching between the A and D blocks at 1900Mhz multiple times per second. As far as the phone and the network are concerned, the group of frequencies licensed are all treated as if they were all in the same group whether they are 800 or 1900Mhz.
Now, the control channel you are using at that moment is always the same until a handoff is necessary. It is only the voice channels that change constantly as your phone is hopping. If you get a Nokia and use its Test Mode, you'll see the channels switching constantly while you're on a call. I haven't seen other brands that show this. Other brands normally just show the control channel which doesn't change if there is no handoff.
Bobolito - .. Thanks!!
I Wasn't aware of the Freq. hopping being used by GSM.
Here's another question (if you know the answer):
If the control channel on AT&T GSM happens to, say, be on 800Mhz, could this cause the call "breakups" I sometimes see posted.... In other words in a pure 800 system, the 800 control channel "knows" your hanset's signal strength back to the tower, but an 800 control channel can't "know" what your 1900 sig strength will be, so if you were to walk inside a building that was still "ok" at 800 but poor at 1900, wouldn't the time packets (voice) portions being switched to 1900 get "lost"??
This would be less of a problem if the control channel was at 1900 since the "other" band (800), would tend to be as good or better off the same tower.....
Here is a link to an AT&T GSM "Choppy/fluttery" breakup post..
hmmm....I see what you're saying, but as far as I know, no one has implemented such a configuration because of the potential problem you described. Normally, systems will have voice channels at 800Mhz before they have a control channel, not the other way around. However, even if the control channel is at 800Mhz and voice is at 1900, the system still knows it is handling voice at 1900 because the mobile reports back to the tower telling it how reception is. Based on this, if you go into a building and lose the 1900Mhz voice channels, the call will automatically switch to an all 800Mhz voice channels/hopping because it will lose the 1900Mhz portion. The tower will know the phone lost the 1900Mhz voice channels because the phone reports it back to the tower.
They don't put control channels on 800 without voice channels for this reason, otherwise the call will drop. With voice channels at 800Mhz as well, they prevent calls from dropping in this particular situation.
.. I thought that the voice channel was for the call, & the control channel determines the "phones" reporting, switching & handoffs ect, & if the control channel is on 800, the tower wouldn't "know" what the phones 1900 reception is, & vice versa.....
Perhaps the recent "choppy" posts can be explained another way -- If AT&T uses both bands for GSM, there will be areas where the 1900 signal is "marginal" 1-2 bars), but not bad enough for the system to drop the 1900, while 800 is fine, & the phone will have this effect, just as there are areas where a single band call will go thru but breakup or be less than perfect.
We may all tend to think the cell system is "smarter" than it is.... Some people (not you or I ), seem to post as if a call will always be either "perfect" or "dropped" with nothing in-between.
I'm sure both Verizon & AT&T will have added coverage & capacity, AND additional "quirks" in the system by overlaying 2 bands in 1 market/system...... I am still curious as to the inner details of how cell systems operate, please post any other info you have or find out in the future on this subject, & I will do the same....
I have lots of questions for my VZW contact next time I see him !! .....
But that is correct. The voice channel just carries the voice during a call and the control channel is used to communicate signal conditions, switching, handoffs, etc. Therefore, that's how the tower "knows" the condition of the reception even if it is in a different band.
As in the previous example, if the CCH is at 800 and the VCH at 1900, the phone reports the status of the 1900 reception to the network all the time. Since it is all in the same network, it doesn't matter which band it is used for reporting. The system or the phone don't care what band you are using because they pay attention to both the quality of the voice channel link and the control channel link.
That makes sense.
I was originally under the impression that the system only paid attention to the quality of the control channel link, to determine phone reception.
I am very curious to see what starts showing up on my 3586i's Test screens once VZW turns on the 1900Mhz channels!!
Info on CDMA systems, pilot/synch/paging/traffic channels, PN offsets, testing equipment etc....
So a lot of this stems around GSM, but is this applicable to TDMA as well? AT&T still has a lot of TDMA users out there using 850 bandwidth. I'm wondering if it is possible to program a TDMA BCS to behave in the same way? i.e.: put the control channels at 850, and then voice at both 850 and 1900? That way both the TDMA and GSM users are able to take advantage of both the benefits of 850 in fringe areas and the extra spectrum available at 1900 when in strong signal areas. My understanding is that most TDMA phones support both 850 and 1900. Is this an option or is TDMA stuck with staying at 1 frequency? It would be nice if AT&T/Cingular could do this to help even out the playing field (so to speak) and make GSM a more attractive option for old-time TDMA customers.
None of the 1900Mhz GSM overlays have included TDMA capability at 1900... AT&T in NY/NJ is GSM only at 1900Mhz..
It Could be done in theory, but I doubt any carriers have plans to add tdma to their newer GSM-only 1900 Systems....
Right...that's not going to happen. The plans are to migrate everyone to GSM. Bringing more capacity to TDMA will only slow down the plans.
By the way, there's nothing stopping you from putting TDMA voice and control channels in separate bands. In fact, I've seen 1900 to 800 (and viceversa) handoffs during the same call on TDMA. Now, TDMA can't do things like Frequency Hopping, dynamic spectrum allocation, slot sharing or variable output based on audio, which are features only used in GSM to save battery energy and conserve network spectrum.
Today i was in a place i knew that sprint NEVER works, and my phone always roams on Verizon. On my new 8200, the phone displays for you the SID, Channel, Technology, and Frequency. My 8200 picked up BOTH verizon DIGITAL 800 mHz AND 1900 mHz. I guess Verizon has 1900 up and running.